This white, foamy oil slick appears almost beautiful in this satellite image — but it's set to become the worst oil spill in U.S. history. The Coast Guard is considering setting it on fire to save the environment.

A Louisiana drill rig exploded and sank last week, and some 42,000 gallons of oil are still leaking out of the rig's underwater well, located about 50 miles off the coast of Louisiana. Eleven rig workers are still missing, presumed dead. Here's a picture of the rig on fire:

British Petroleum, the owner of the rig, is racing to shut down the well using eight remote-controlled submarines, but hasn't had any success yet. The Coast Guard says this may be the worst spill in U.S. history. The "controlled burn", using fireproof booms, could happen as soon as Wednesday — because the slick is in danger of encroaching on sensitive ecological areas in the Mississippi Delta. So far, the slick's come about 20 miles from land. Here's a NASA satellite image showing the slick as of Sunday:

Robot submarines or controlled ignition: Which method of containing the disaster will succeed?